1. Field of the Invention
The present invention relates to sound isolation devices, and more particularly to resilient grommets for attenuating exhaust noise from the body of an automobile.
2. Description of the Prior Art
The operation of a motor vehicle invariably entails the emission of exhaust noise. This noise is then directed and confined to the exhaust pipes and the muffler wherein it is acoustically cancelled or attenuated. In practice the exhaust pipe extends from the internal combustion engine in the motor vehicle to the muffler suspended from its lower surfaces. Since an internal combustion engine is resiliently mounted to the vehicle the exhaust system acts as an efficient carrier of mechanical noise associated with the vibrations of the engine and the acoustic noise of internal combustion. In consequence great attention must be exercised in isolating the exhaust system from the body panels of the vehicle. Simply, unless the mechanical transfer of noise is attended the whole purpose of the muffler is defeated since the large body panels of the vehicle are extremely efficient in converting mechanical energy back to acoustic form.
Accordingly various resilient mounting arrangements have been devised in the past which effectively isolate the exhaust system from the vehicle frame. In one form such resilient mounting arrangements include one or more elastomeric grommets surrounding the fasteners of the exhaust mounts. Thus the prior art includes a variety of annular grommet examples useful for this purpose. In each instance, however, the grommet alignment presents installation difficulty and those engaged in exhaust system repairs often expend substantial labor in effecting proper mounting.
A resilient grommet assembly which effects installation alignment and alignment with use is therefore extensively sought and it is one such assembly that is disclosed herein.